Fatty acid esters of ethoxylated alkylglucosides

ABSTRACT

A mixture of fatty acid esters of ethoxylated alkylglucosides of formula I is useful as a refatting agent in cosmetic formulations.

This application is a 371 of PCT/10503/18720 filed Jun. 13, 2003 whichclaims benefit of 60/390,074 filed Jun. 19, 2002.

The present invention relates to a mixture of fatty acid esters ofethoxylated alkylglucosides and their use in cosmetic compositions.

BACKGROUND OF THE INVENTION

Glucose derivatives, such as fatty acid esters of alkoxylatedalkylglucosides, may be produced from renewable raw materials. Due toagricultural over-production the starting materials are low in cost andavailable in unlimited amounts. Therefore, much research efforts havebeen spent on the development of ethoxylated alkylglucosides and theiruses.

U.S. Pat. No. 4,364,930 discloses a stable oil-in-water emulsion for usein cosmetic or pharmaceutical compositions. The emulsifying systemcomprises among other components a mixture of (1) mono- and/or dialkylcarboxylates of alpha-methyl glucoside and (2) mono- and/or dialkylcarboxylates of alpha-methyl glucoside which has been polyoxyethylenatedwith 10-30 moles of ethylene oxide.

U.S. Pat. No. 5,502,175 discloses fatty acid esters which are preparedby ethoxylating methylglucoside with from 84 to 300 moles, preferably120 moles of ethylene oxide and subsequent esterification with 2-4moles, preferably 1.8-3.5 moles of a saturated or unsaturated C1 fattyacid. The prepared fatty acids are used in shampoos and foam baths. Theyact as a thickening agent and have a good moisturizing effect and reduceirritation values of common ingredients, such as anionic and non-ionicsurfactants.

U.S. Pat. No. 4,687,843 discloses esterified propoxylated methylglucoside 25 compositions which are useful as skin moisturizers andemollients.

One object of the present invention is to find new acid esters ofalkoxylated alkylglucosides. Another object of the present invention isto find acid esters of atkoxylated alkylglucosides which are useful inskin conditioning, and in particular as an enhancer of skin lipids, thatmeans as a refatting agent.

SUMMARY OF THE INVENTION

One aspect of the present invention is a mixture of fatty acid esters ofan ethoxylated alkylglucoside of formula I

wherein the sum of A, B, C and D is from 10 to 60, each R₁, R₂, R₃ andR₄ independently is hydrogen or —C(O)-M, wherein M is a C₁₁-C₂₉ alkyl oralkenyl, and R₅ is a C₁-C₅ alkyl, provided that the ethoxylatedalkylglucoside on the average comprises from 2.1 to 2.8—C(O)-M groups.

Another aspect of the present invention is a cosmetic composition whichcomprises the mixture of fatty acid esters.

Yet another aspect of the present invention is the use of the mixture offatty acid esters as a refatting agent in a cosmetic composition.

Yet another aspect of the present invention is a process for preparingthe mixture of fatty acid esters, which process comprises the steps of

i) reacting an alkylglucoside with from 10 to 60 moles of ethylene oxideper mole of alkylglucoside and

ii) reacting the ethoxylated alkylglucoside with from 2.1 to 2.8 molesof a saturated or unsaturated C₁₁-C₂₉ fatty acid or a C ester thereof.

DETAILED DESCRIPTION OF THE INVENTION

The fatty acid esters of the ethoxylated alkylglucosides of the presentinvention are a mixture of molecules with different degrees ofesterification such that the compounds of formula I on the averagecomprise from 2.1 to 2.8, preferably from 2.2 to 2.7, more preferablyfrom 2.3 to 2.5, most preferably about 2.4—C(O)-M groups.

Generally the degree of ethoxylation of the individual molecules alsovaries somewhat, as it is typical for oligomers. However, the averagedegree of ethoxylation, that means the sum of A, B, C and D is from 10to 60, preferably from 25 to 50, more preferably from 30 to 40, mostpreferably about 35. A, B, C and D each independently can have themeaning of from 0 to 60, provided that the sum of A, B, C and D is from10 to 60.

In formula I M is C₁₁-C₂₉ alkyl or alkenyl, preferably C₁₁-C₁₉ alkyl oralkenyl, more preferably C₁₆-C₁₈ alkenyl, most preferably a C₁₇ alkenylgroup. The alkyl and alkenyl group may be branched, but preferably it isstraight.

In formula I R₅ is an alkyl group of from 1 to 5 carbon atoms,preferably from 1 to 3 carbon atoms, most preferably methyl.

The fatty acid esters of the present invention can be prepared bypreparing first a mixture of fatty acid esters of an alkylglucoside andthen ethoxylating the product. However, according to a preferred processthe fatty acid esters are prepared by ethoxylating an alkylglucoside andsubsequent esterification.

The ethoxylation can be accomplished in one, two or more steps. Thereaction temperature generally is from 100 to 190° C., preferably from130 to 160° C., more preferably from 145 to 155° C. The reactionpressure generally is from 100 to 1000 kPa, preferably from 200 to 600kPa, more preferably from 250 to 550 kPa.

When carrying out the ethoxylation step in one step, an alkylglucoside,preferably methylglucoside, is ethoxylated with from 10 to 60,preferably from 25 to 50, more preferably from 30 to 40, most preferablywith about 35 moles of ethylene oxide per mole of the alkylglucoside.Generally a basic catalyst is used, preferably an alkali metalhydroxide, more preferably potassium or sodium hydroxide. The amount ofcatalyst generally is from 0.2 to 5 weight-percent, preferably from 0.5to 2.5 weight-percent, based on dry alkylglucoside. The ethoxylation isgenerally conducted under an inert atmosphere using a gas like argon,helium, or preferably nitrogen. The ethoxylation is generally completedwithin 2 to 6 hours.

In an alternate embodiment of the present invention the ethoxylation isaccomplished in two steps. An ethoxylated alkylglucoside whichpreferably comprises from 5 to 25 moles, more preferably from 10 to 20moles, most preferably about 20 moles of groups derived from ethyleneoxide per mole of alkylglucoside, is used as starting material forfurther ethoxylation. The preferred starting materials are commerciallyavailable from Amerchol Corp. under the trademark Glucam E-10 or GlucamE-20. The ethoxylated alkylglucoside is converted to the correspondingalkoxide salt by reacting the ethoxylated alkylglucoside with a base,preferably an alkali metal hydroxide, most preferably with potassium orsodium hydroxide. The alkali metal hydroxide is preferably used as a 0.1to 1 weight percent, more preferably 0.25 to 0.5 weight percent, aqueoussolution. The ethoxylation is carried out as described above with acorresponding smaller amount of ethylene oxide.

The subsequent esterification is effected by direct esterification withfrom 2.1 to 2.8, preferably from 2.2 to 2.7, more preferably from 2.3 to2.5, most preferably about 2.4 moles of a fatty acid or bytransesterification with a corresponding amount of a fatty acid ester.

The fatty acid used for direct esterification is a saturated orunsaturated C₁₁-C₂₉ fatty acid, preferably a C₁₁-C₁₉ fatty acid, morepreferably a C₁₆-C₁₈ fatty acid or a blend of such fatty acids.Preferred fatty acids are stearic acid, linoleic acid, linolenic acid,lauric acid, palmitic acid, undecanoic acid, or most preferably oleicacid. The direct esterification with a saturated or unsaturated C₁₁-C₂₉fatty acid can be carried out according to a process known in the art,for example by an acid catalyzed reaction.

For transesterification C₁₋₄-alkyl esters of the mentioned C₁₁-C₂₉ fattyacids are preferred, more preferably the methyl esters of the mentionedC₁₁-C₂₉ fatty acids. Methyl oleate is the most preferred fatty acidester. The transesterification is generally conducted in the presence ofa base catalyst. The catalyst is preferably an alkali metal hydroxide,such as potassium or sodium hydroxide. Generally from 0.03 to 1 weightpercent, preferably from 0.1 to 0.5 weight percent of base catalyst isused, based on the weight of ethoxylated alkylglucoside. The reactiontemperature generally is from 130 to 200° C., preferably from 160 to185° C., more preferably from 170 to 180° C. The reaction is preferablyconducted under vacuum. More preferably, the vacuum starts at about 125mm Hg and ends at about 3 mm Hg. The reaction typically takes about 4 to6 hours.

The above-described mixture of fatty acid esters is useful in cosmeticcompositions, particularly in skin cleansing compositions. Cleansing theskin does not only remove dirt but also removes fats and oils, whichleaves the skin feeling dry and taut. Therefore, the cosmetic industryspends much research efforts to find conditioning agents which areuseful in skin cleansing compositions. This presents a major challenge,since a refatting agent should fulfill a variety of requirements. Itshould enhance skin lipids by leaving the skin smoother, less dry, and acausing a positive tactile sensation. It should not unduly increase theviscosity of the cleansing composition, otherwise the cleansingcomposition is not pourable and not accepted by the consumers. Also, therefatting agent should not provide an unpleasant odor or color to thecleansing composition. It should not adversely affect clarity or foamingand be compatible with other cleansing ingredients.

It has surprisingly been found that the above-described mixture of fattyacid esters of ethoxylated alkylglucosides is useful as a refattingagent in cosmetic formulations, such as skin cleansing compositions. Themixture of fatty acid esters is generally a clear or slightly hazyliquid with a viscosity low enough to be pourable. It has generally alight yellow color.

The cosmetic composition of the present invention generally comprisesfrom 0.1 to 10, preferably from 0.5 to 5, more preferably from 1 to 3weight percent of the mixture of fatty acid esters, based on the totalweight of the cosmetic composition. Cosmetic compositions comprising thepreferred fatty acid esters of the present invention have shownfavorable results in sensory assessments wherein after-feel in skinwashing tests are evaluated. It has also been found that the mixture offatty acid esters does not adversely affect the foaming of cleansingformulation, but produces a creamier foam.

The cosmetic composition of the present invention may comprise a numberof additives known in the art, such as water, surfactants, thickeners,conditioning agents, humectants, preservatives, perfumes, and colorants.

The present invention is further illustrated by the following exampleswhich should not be construed to limit the scope of the presentinvention. All parts and percentages are by weight unless otherwiseindicated.

EXAMPLE 1

A 1.5 liter glass pressure reactor, equipped to automatically feedethylene oxide based on pressure, is charged with 589 g of ethoxylatedmethylglucoside (comprising 20 moles of ethylene oxide units per mole ofmethylglucoside) which contains about 0.25 weight percent potassiumhydroxide. The contents of the reactor are heated and the reactor isevacuated when the temperature of the contents reaches about 130° C.Heating is continued. When the temperature of the reactor contentsreaches about 145° C., the reactor is pressurized with nitrogen to about450 kPa (about 50 psig). The pressure is released to about 180 kPa(about 10 psig). This nitrogen pressurizing and releasing is repeatedtwice more. The reactor is then pressurized to about 275 kPa (about 23psig). When the temperature of the contents reaches 155° C., ethyleneoxide is fed into the reactor. The ethylene oxide feed rate iscontrolled so that the reactor pressure never exceeds about 550 kPa(about 65 psig). After about 376 g of ethylene oxide have been feed tothe reactor, the ethylene oxide feed is stopped and the reactor is heldat 155° C. for 30 minutes to essentially react any remaining ethyleneoxide. The reaction is cooled and the contents discharged to yield about965 g of recovered ethoxylated alkylglucoside comprising about 35 unitsderived from ethylene oxide per unit of alkylglucoside. The product isdesignated as E-35.

For esterification of the ethoxylated alkylglucoside a laboratory roundbottom glass reactor is charged with 100 grams of E-35 as preparedabove, 41 g of methyl oleate, and 0.1 g of hypophosphorous acid. Anitrogen sparge is initiated and the contents of the reactor are heatedto 175° C. while applying vacuum. The vacuum is about 125 torrs. Thereaction is held at 175° C. with this vacuum for 30-60 minutes. Thevacuum is then slowly increased to maximum, about 3 torrs and thereaction held under these conditions for about 4 to 5 hours. Thereaction mixture is cooled. Once its temperature is below 80° C., it isneutralized with about 0.4 g of 88% aqueous lactic acid. The reactorcontents are discharged and about 138 g of product are recovered. Basedon weights charged, the product can be described as a mixture of fattyacid esters of ethoxylated methylglucoside comprising on average 35moles of groups derived from ethylene oxide and on average 2.4 moles ofester groups per mole of methylglucoside.

The product is a slightly viscous, clear liquid and light yellow incolor.

EXAMPLE 2

Example 1 is repeated except that that only about 37.6 grams of methyloleate is used. The produced mixture of fatty acid esters of ethoxylatedmethyl glucoside comprises on average 35 moles of groups derived fromethylene oxide and on average 2.2 moles of ester groups per mole ofmethylglucoside.

EXAMPLE 3

Example 1 is repeated except that 47.8 grams of methyl oleate is used.The produced mixture of fatty acid esters of ethoxylated methylglucosidecomprises on average 35 moles of groups derived from ethylene oxide andon average 2.8 moles of ester groups per mole of methylglucoside.

Refatting Tests

The products of Examples 1-3 above are compared in a sensory test withPEG-7 Glycerol Cocoate (polyoxyethylene (7) glyceryl monococoate), whichis commercially available as Cetiol HE (Trademark) from Cognis, andwhich is a leading refatting agent in the US market.

A formulation consisting of 9% sodium laureth-2 sulfate, commerciallyavailable as Standapol ES-2 (Trademark) from Cognis; 4% cocamidopropylbetaine, commercially available as Velvetex BK-35 (Trademark) fromCognis, 1% decyl glucoside, commercially available as Plantaren 2000(Trademark) from Cognis, and 85% water is prepared.

To produce the formulation of Examples 1-3, 1% of the product of Example1, 2 or 3 is added to the formulation. To produce the formulation ofComparative Example A, 1% of Cetiol HE (Trademark) is added to theformulation.

A panel study of 20 people is conducted. Initially the panelist washesboth hands with Ivory (Brand name) soap bar, and then places a latexglove on one hand and washes the other hand with approximately one gramof either the formulation of one of the Examples 1-3 or with theformulation of Comparative Example A. The panelist notes the quality andquantity of foam and feel of the foam. The panelist then places a gloveon the other hand and repeats the procedure with the other formulation,noting again the quality and quantity of the foam and feel of the foam.

The panelist rinses both hands, pats dry, and once fully dried,determines the feel of each hand with the other to determine anydifference in after-feel. The percentage of people expressing apreference for the formulation of Example 1, 2 or 3 respectively overthe formulation of Comparative Example A, the percentage of peopleexpressing a preference for the formulation of Comparative Example A andthe percentage of people expressing no preference are listed in Table 1below.

Evalulation foam quantity and quality After-feel sensory evaluationPreference Preference for No Preference for Preference No Example forinvention Comp. Ex. A preference Comp. Ex. A for invention preference 155 40 5 33 27 40 2 40 55 5 15 35 50 3 55 40 5 35 20 45

1. A mixture of fatty acid esters of an ethoxylated alkylglucoside offormula I

wherein the sum of A, B, C and D is from 30 to 40, each R₁, R₂, R₃, andR₄, independently is hydrogen or —C (O)—M, wherein M is a C₁₁-C₂₉ alkylor alkenyl, and R₅ is a C₁-C₅ alkyl, provided that the ethoxylatedalkylglucoside on the average comprises from 2.1 to 2.8-C(O)—M groups.2. The mixture of claim 1 wherein the ethoxylated alkylglucoside on theaverage comprises from 2.3 to 2.5-C (O)—M groups.
 3. The mixture ofclaim 1 wherein M in formula I is a C₁₇ alkenyl group.
 4. The mixture ofclaim 1 wherein R₅ is methyl.
 5. A cosmetic composition comprising themixture of fatty acid esters of claim
 1. 6. The cosmetic composition ofclaim 5 being a skin cleansing composition.
 7. A method of using themixture of fatty acid esters of claim 1 as a refatting agent in acosmetic composition.
 8. A process for preparing the mixture of claim 1comprising the steps of: i) reacting an alkylglucoside with from 30 to40 moles of ethylene oxide per mole of alkylglucoside and ii) reactingthe ethoxylated alkylglucoside with from 2.1 to 2.8 moles of a saturatedor unsaturated C₁₁-C₂₉ fatty acid or a C¹⁻⁴-alkyl ester thereof.